Preheat oven to 375F.
Spread cubed bread on a sheet pan and toast in oven, about 5 min. Set aside.
Puree carrot, onion, and celery in a blender or food processor until it becomes a fine pulp. Set aside.
Set a large sauté pan to medium heat and add chorizo. Cook vegan chorizo stirring frequently until slightly brown, about 5-7 min. Remove from pan and set aside.
Add vegetable puree to sauté pan, reduce heat to low, and cook until almost dry, about 7 minutes. Remove from pan and set aside.
In a large bowl combine chorizo, vegetable puree, bread, 1/3 cup of chestnuts, and chopped sage.
In a medium bowl combine 1 tbsp. ground flax seed and 2 ½ tbsp. of water and let sit for 5 minutes. Pour in vegetable stock, salt, and almond milk and whisk well. Pour this over bread mixture and fold to combine.
Place mixture in an 8 x 12 baking dish, and bake for 30 min. uncovered, or until top is golden brown.